1. Field of the Invention
The present invention is related to a printed wiring board and its manufacturing method, especially to a wiring board having a penetrating hole and to its manufacturing method.
2. Discussion of the Background
In Japanese Laid-Open Patent Publication 2006-41463, a method is disclosed to form a through-hole in a substrate by forming a penetrating hole with a cross section of an hourglass-shape (the shape of a traditional Japanese hand-drum) and by performing plating to fill metal in the penetrating hole. The penetrating hole with an hourglass-shaped cross section is made up of a first cone-shaped blind hole formed on one side of the substrate and a second cone-shaped (in a shape of a hand-drum) blind hole formed on the other side of the substrate. The contents of this publication are incorporated herein by reference in their entirety.